Vane pump with variable discharge volume

ABSTRACT

The present invention relates to a vane pump with variable discharge volume, and comprising a pump housing; a cam ring having an elliptical cross-section for its inner circumference and outer circumference to form a compression chamber wherein a compression medium is compressed, and is accommodated in said pump housing so that it may rote; a rotor hat is accommodated such that a plurality of vanes may appear frequently on the outer circumference to undergo rotations in the compression chamber of said cam ring and compress said compression medium; and a cam ring rotation controller that contacts the outer circumference of said cam ring, and rotates said cam ring if the discharge pressure of said compression medium is equal to or more than its pressure setting and stops the rotation of said cam ring if the discharge pressure of said compression medium is less than its pressure setting to control rotations of said cam ring. Accordingly, the rotation and stoppage of rotation of the cam ring is accomplished based on changes in the discharge pressure, to enable variation in discharge volumes, and enhancement of discharge efficiency.

TECHNICAL FIELD

The present invention relates to a vane pump with a variable discharge volume, and in particular to a vane pump with a variable discharge volume in which the discharge volume changes depending on a difference in the revolutions of a rotor and a cam ring.

BACKGROUND ART

A conventional vane pump is constituted, with a cam ring being fixed at an inner side of pump housing. A suction side plate and a discharge side plate are installed at both front and rear sides of a cam ring, respectively.

In addition, an almost elliptical compression chamber in which a compressed medium is compressed is formed in the interior of the cam ring.

A rotor supported by a driving shaft is rotatably supported in the compression chamber of the interior of the cam ring, with a plurality of vane grooves being formed on an outer surface of the rotor. A vane is retractable through each vane groove, reciprocating in a radius direction in the vane groove.

In the above conventional vane pump, a front end portion of each vane comes into contact with an almost elliptical inner surface of the cam ring with the aid of a centrifugal force depending on the rotation of the rotor, according to which a compressed medium such as oil is sucked via the suction side plate into a compression chamber of the cam ring, and the sucked compressed medium is compressed upon the decrease of the volume of the interior of the cam ring and is discharged via the discharge side plate.

Since the conventional vane pump is configured like the cam ring is fixed at the pump housing, the suction region and the discharge region formed between the rotor at the interior of the cam ring and the elliptical inner space of the cam ring, namely, in the compression chamber remain constant.

In the conventional art, it is almost impossible to change the suction region and the discharge region depending on the change of pressure.

In the high pressure state that the removal volume becomes maximum, over volume of fluids is discharged, and at a low pressure, fluids exceeding necessary volume are discharged, thus decreasing the efficiency of the pump.

DISCLOSURE OF INVENTION

Accordingly, it is an object of the present invention to provide a variable discharge volume vane pump which makes it possible to change the volume of discharge and enhance discharge efficiency by rotating a cam ring or stopping the rotation of the same depending on a change in a discharge pressure.

To achieve the above objects, there is provided a vane pump with a variable discharge volume, comprising a pump housing; a cam ring of which inner and outer surfaces each have an elliptical cross section and which has a compression chamber for compressing a compressed medium and is rotatably accommodated in the pump housing; a rotor which rotates in the compression chamber of the cam ring and compresses the compressed medium, with a plurality of vanes being formed in a radial shape on its outer surface and each being retractable; and a cam ring rotation controller which comes into contact with an outer surface of the cam ring and rotates the cam ring when a discharge pressure of the compressed medium is higher than a set level and stops the rotation of the cam ring when a discharge pressure of the compressed medium is lower than a set level, thus controlling the rotation of the cam ring.

Here, the cam ring rotation controller comprises a piston which comes into slidable contact with an outer surface of the cam ring and reciprocates depending on the rotation of the cam ring; and a spring which provides an elastic force to the piston to stop the rotation of the cam ring when a discharge pressure of the compressed medium is lower than a set level.

When a discharge pressure of the compressed medium is higher than a set level, the cam ring rotates, and the piston moves toward the spring, thus compressing the spring.

The cylinder control controller further comprises a spring adjusting bolt for adjusting the displacement of the spring.

There is further provided a rod which is disposed between the piston and the spring and ascends and descends by means of a discharge pressure of the compressed medium, thus transferring an elastic force of the spring to the piston, and inclined parts having opposed inclination directions are formed at the end portions of the piston and the rod in which the piston and the rod come into contact with each other.

There are further provided a suction side plate which forms a suction passage for guiding a suction of a compressed medium into the compression chamber and is formed at one side of the cam ring; and a discharge side plate which forms a discharge passage for guiding the discharge of the compressed medium compressed in the compression chamber and is installed opposite to the suction side plate about the cam ring.

EFFECTS

In the present invention, it is possible to change the volume of discharge and enhance discharge efficiency by rotating a cam ring or stopping the rotation of the same depending on a change in a discharge pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein;

FIG. 1 is a cross sectional view illustrating a variable discharge volume vane pump according to a first embodiment of the present invention;

FIG. 2 is a disassembled perspective view illustrating major parts of FIG. 1;

FIG. 3 is a perspective view illustrating an engagement of FIG. 1;

FIGS. 4 and 5 are cross sectional views illustrating the operation procedures of a cam ring and a cam ring rotation controller of a variable discharge volume vane pump according to a first embodiment of the present invention; and

FIGS. 6 and 7 are cross sectional views illustrating the operation procedures of a cam ring and a cam ring rotation controller of a variable discharge volume vane pump according to a second embodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

The preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Throughout the descriptions, the same elements having the same constructions are given the same reference numerals. The first embodiment is to be described as a representative among many embodiments. In other embodiments, only the other constructions different from the first embodiment will be described.

FIGS. 1 to 5 are views illustrating a variable discharge volume vane pump according to a first embodiment of the present invention. The variable discharge volume vane pump according to a first embodiment of the present invention comprises a pump housing 11, a cam ring 21 which is rotatably accommodated in the pump housing 11, a rotor 25 compressing a compressed medium, and a cam ring rotation controller 31 changing the discharge volume of a compressed medium by controlling the rotation of the cam ring 21.

The pump housing 11 comprises a suction port 13 for sucking a compressed medium into the compression chamber 23.

A cam ring 21 is rotatably accommodated in the interior of the pump housing 11. A compression chamber 23 is formed in the interior of the cam ring 21 for compressing a compressed medium. The inner surface of the ca ring 21 has an elliptical cross section. A vane 29 of the rotor 25, which will be described later, comes into contact with the inner surface of the cam ring 21. At an outer surface of the cam ring 21 of the variable discharge volume pump according to the present invention is formed a protrusion 21 a having at least one maximum curvature radius. A piston 33 slides and contacts with an outer surface of the cam ring 21. The inner and outer surfaces of the cam ring 21 each have an elliptical cross section.

A rotor 25 is rotatably installed in the interior of the cam ring 21, with the rotor 25 being supported by a driving shaft 5 of the motor in the compression chamber 23 of the cam ring 21 and compressing a compressed medium. A plurality of vane grooves 27 are formed on an outer surface of the rotor 25 in a radius direction. A vane 29 coming into contact with the inner surface of the cam ring 21 operates retracting via the vane groove 27. The vane 29 comes into contact with an inner surface of the cam ring 21 and reciprocates in a radius direction of the rotor 25.

The cam ring rotation controller 31 comes into contact with an outer surface of the cam ring 21, thus controlling the rotation of the cam ring 21. The cam ring rotation controller 31 comprises a piston 33 which slide-contacts with an outer surface of the cam ring 21 and reciprocates based on the rotation of the cam ring 21, and a spring 35 which provides an elastic force to the piston 33 to stop the rotation of the cam ring 21 when a discharge pressure of the compressed medium exceeds a set pressure.

As shown in FIGS. 4 and 5, an end portion of the piston 33 comes into close contact with an outer surface of the cam ring 21, and the other end portion of the piston 33 is supported by the spring 35. The piston 33 compresses and decompresses the spring 35 depending on the rotation of the cam ring 21.

The spring 35 according to an embodiment of the present invention has a coil shape, and the spring 35 is accommodated in the spring accommodation part 15 formed at the pump housing 11. An end portion of the spring 35 supports the piston 33, and the other end portion of the spring 35 is accommodated in the spring accommodation part 15 with the aid of the spring support plate 37.

When the discharge pressure of the compressed medium exceeds a set level, the piston 33 moves toward the spring 35 with the aid of the rotation of the cam ring 21, according to which the spring 35 is compressed, and when the discharge pressure of the compressed medium is less than the set level, the cam ring 21 stops rotating as the piston 33 pressurizes the outer side of the cam ring 21 with the aid of the elastic force of the spring 35.

The elastic force of the spring 35 can be controlled by a spring adjusting bolt 39. The spring adjusting bolt 39 is engaged to a spring support plate 37, thus adjusting a displacement of the spring 35 accommodated in the spring accommodation part 15 by compressing or decompressing the other end portion of the spring 35, which results in changing the elastic force of the spring 35 of which elastic force is applied to the piston 33.

In addition, the variable discharge volume vane pump according to the present invention is configured like the suction side plate 51 and the discharge side plate 55 are opposite to each other with respect to the cam ring 21.

The suction side plate 51 is disposed at one side of the cam ring 21 and has a suction passage 53 for sucking a compressed medium into the compression chamber 23.

The discharge side plate 55 is disposed at the other side of the cam ring 21 and has a discharge passage 57 for guiding of the discharge of the compressed medium compressed in the compression chamber 23.

Here, reference numeral 61 represents a discharge guide for discharging the compressed medium passed from the compression chamber 23 via the discharge side plate 55. A discharge port guide 61 might be divided into two parts, with each discharge guide 61 being equipped with a nipple 62.

Reference numeral 63 represents a main cover for covering one side of the pump housing 11, and 65 represents an auxiliary cover for covering the other side of the pump housing 11. Reference numeral 67 represents a bearing for supporting a trust load respectively applied to the suction side plate 51 and the discharge side plate 55, and 69 represents a driving shaft bearing for rotatably supporting the driving shaft 5. 71 represents a packing for sealing the interior of the pump housing 11, and 73 represents an O-ring for sealing the main cover 63 and the auxiliary cover 65.

According to the above construction, the variable discharge volume vane pump according to the first embodiment of the present invention operates in such a manner that when the rotor 25 rotates depending on the operation of the driving shaft 5, the front end portion of the vane 29 of the rotor 25 rotates coming into contact with the inner surface of the compression chamber 23 of the cam ring 21 with the aid of a centrifugal force.

The compressed medium is sucked into the compression chamber 23 of the cam ring 21 via the suction passage 53 of the suction side plate 51 via the suction port 13 and is compressed by a decreasing volume depending on the rotation of the rotor 25 and is discharged via the discharge passage 57 of the discharge side plate 55.

As the rotor 25 rotates, the compressed medium is compressed and discharged, and the cam ring 21 rotates in a rotation direction of the rotor 25. When the discharge pressure is getting higher, the rotation force of the cam ring 21 increases.

When the discharge pressure of the compressed medium is higher than a set level, the rotational force of the cam ring 21 becomes larger than the frictional force between the piston 33 and the outer surface of the cam ring 21, so the cam ring 21 rotates, and as shown in FIG. 4, the piston 33 which keeps pressurizing the outer surface of the cam ring 21 slides along the outer surface of the cam ring 21 and moves toward the spring 35, thus compressing the spring 35. At this time, the discharge volume of the medium compressed in the compression chamber 23 can changed with the aid of a difference in the revolutions between the rotor 25 and the cam ring 21. When the rotor 25 and the cam ring 21 rotate at the same revolutions, the compression of the compressed medium does not occur at the compression chamber 23 of the cam ring 21, thus stopping the discharge.

On the contrary, when the discharge pressure of the compressed medium is lower than the set level, the rotational force of the cam ring 21 becomes smaller than the frictional force between the piston 33 and the outer surface of the cam ring 21, so the piston 33 does not move toward the spring 35, and as shown in FIG. 5, the piston 33 does not travel beyond the protrusion 21 a having the highest curvature radius of the outer surface of the cam ring 21, according to which the cam ring 21 stops rotating. At this time, when the rotor 25 rotates, the compressed medium is compressed in the compression chamber 23 of the cam ring 21, as a result of which the discharge volume becomes highest.

As one example, when the rotor 25 rotates 10 turns, and the cam ring 21 rotates 10 turns, the discharge stops, and the discharge volume becomes zero. When the rotor 25 rotates 10 turns, and the ca ring 21 rotates 5 turns, the discharge volume becomes 50%. When the rotor 25 rotates 10 turns, and the cam ring 21 stops, the discharge volume becomes 100%.

The variable discharge volume vane pump according to a first embodiment of the present invention is basically directed to varying the discharge volume of the medium which is compressed by the compression chamber 23 and discharged, thus enhancing the efficiency of discharge, in such a manner that the am ring 21 rotates or stops depending on the change of set discharge pressure of the compressed medium, namely, with the aid of a difference in the revolutions between the rotor 25 and the cam ring 21.

FIGS. 5 and 6 are views illustrating the variable discharge volume vane pump according to a second embodiment of the present invention. The variable discharge volume vane pump according to the second embodiment of the present invention is disposed between the piston 33 and the spring 35, as compared to the first embodiment, with a rod 41 being further provided for providing the elastic force of the spring 35 to the piston 33.

The piston 33 is installed at the pump housing 11 and reciprocates in a compression direction of the spring 35. The rod 41 is disposed between the piston 33 and the spring 35 and is disposed at the spring accommodation part 15 formed at the pump housing 11 and reciprocates therein. A plurality of rollers 43 are slidably engaged at an outer surface of the rod 41.

An inlet flow path 17 communicates with the spring accommodation part 15 for receiving the compressed medium from the compression chamber 23.

Inclined parts 33 a and 41 a are formed at each end portion of the piston 33 and the rod 41 contacting with the piston 33 and the rod 41, respectively, with the inclined parts having opposite inclinations by which the piston 33 reciprocates along with the reciprocation of the rod 41.

The rod 41 moves up and down in the spring accommodation part 15 with the aid of the discharge pressure of the compressed medium from the compression chamber 23, and the inclined part 41 a of the rod 41 ascends and descends along the inclined part 33 a of the piston 33, according to which the piston 33 gets closer to the compression chamber 23 or gets far away from the same, thus rotating or stopping the cam ring 21 depending on the change in discharge pressure.

With the above construction, the variable discharge volume vane pump according to the second embodiment of the present invention is characterized in that when the rotor 25 rotates, the vane 29 of the rod 25 rotates, contacting with an inner surface of the compression chamber 23 of the cam ring 21 with the aid of the centrifugal force, and the compressed medium sucked into the compression chamber 23 is compressed depending on the decreasing volume based on the rotation of the rotor 25 and is discharged via the discharge passage 57 of the discharge side plate 55.

As the rotor 25 rotates, and the compressed medium is compressed and discharged, the cam ring 21 rotates in the rotation direction of the rotor 25. When the discharge pressure is getting higher, the rotational force of the cam ring 21 increases. At this time, part of the discharged compressed medium is inputted into the inlet flow path 17 formed at the pump housing 11, thus ascending and descending the rod 41.

When the discharge pressure of the compressed medium is higher than the set level, the rotational force of the cam ring 21 becomes higher than the frictional force between the piston 33 and the cam ring 21, according to which the cam ring 21 rotates, and the rod 41 is pushed upward with the aid of the discharge pressure of the compressed medium introduced into the inlet flow path 17. The inclined part 33 a of the piston 33 comes into close contact with the inclined part 41 a of the rod 41. As shown in FIG. 6, the piston 33, which keeps pressurizing the outer surface of the cam ring 21, moves toward the outer side of the pump housing 11 while sliding along the outer surface of the cam ring 21. At this time, the discharge volume of the medium compressed in the compression chamber 23 can change depending on a difference in the revolutions between the rotor 25 and the cam ring 21. When the rotor 25 and the cam ring 21 rotate at the same revolutions, since the compression of the compressed medium does not occur in the compression chamber 23 of the cam ring 21, thus stopping discharging.

When the discharge pressure of the compressed medium is lower than the set level, the rotational force of the cam ring 21 becomes smaller than the frictional force between the piston 33 and the outer surface of the cam ring 21, and at the same time the rod 41 does not move upwards with the aid of the discharge pressure of the compressed medium introduced in the inlet flow path 17. As shown in FIG. 7, the piston 33 pressurizes the outer surface of the cam ring 21, and the piston 33 does not move beyond the protrusion 21 a having the highest curvature radius of the outer surface of the cam ring 21, thus stopping the rotation of the cam ring 21. At this time, when the rotor 25 rotates, the compressed medium is compressed in the compression chamber 23 of the cam ring 21, so the discharge volume becomes highest.

The variable discharge volume vane pump according to the second embodiment of the present invention is characterized in that the cam ring 21 rotates or stops depending on the change of the set discharge pressure of the compressed medium, namely, the discharge volume of the medium compressed and discharged from the compression chamber 23 can change due to a difference in the revolutions between the rotor 25 and the cam ring 21, thus enhancing the efficiency of discharge.

The present invention comprises a cam ring of which inner and outer surfaces have almost elliptical cross sections and which forms a compression chamber for compressing the compressed medium and is rotatably accommodated in the pump housing, a rotor which rotates in the compression chamber and pressurizes the compressed medium, and a cam ring rotation controller 31 which rotates the cam ring when the discharge pressure of the compressed medium is higher than a set level, and stops the rotation of the cam ring when the discharge pressure of the compressed medium is lower than a set level, thus controlling the rotation of the cam ring which leads to enhancing the efficiency of the discharge.

As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims. 

1. A vane pump with a variable discharge volume, comprising: a pump housing: a cam ring of which inner and outer surfaces each have an elliptical cross section and which has a compression chamber for compressing a compressed medium and is rotatably accommodated in the pump housing: a rotor which rotates in the compression chamber of the cam ring and compresses the compressed medium, with a plurality of vanes being formed in a radial shape on its outer surface and each being retractable; and a cam ring rotation controller which comes into contact with an outer surface of the cam ring and rotates the cam ring when a discharge pressure of the compressed medium is higher than a set level and stops the rotation of the cam ring when a discharge pressure of the compressed medium is lower than a set level, thus controlling the rotation of the cam ring.
 2. A vane pump with a variable discharge volume according to claim 1, wherein said cam ring rotation controller comprises: a piston which comes into slidable contact with an outer surface of the cam ring and reciprocates depending on the rotation of the cam ring; and a spring which provides an elastic force to the piston to stop the rotation of the cam ring when a discharge pressure of the compressed medium is lower than a set level.
 3. A vane pump with a variable discharge volume according to claim 2, wherein when a discharge pressure of the compressed medium is higher than a set level, the cam ring rotates, and the piston moves toward the spring, thus compressing the spring.
 4. A vane pump with a variable discharge volume according to claim 2, wherein said cylinder control controller further comprises a spring adjusting bolt for adjusting the displacement of the spring.
 5. A vane pump with a variable discharge volume according to claim 2, further comprising: a rod which is disposed between the piston and the spring and ascends and descends by means of a discharge pressure of the compressed medium, thus transferring an elastic force of the spring to the piston, and inclined parts having opposed inclination directions are formed at the end portions of the piston and the rod in which the piston and the rod come into contact with each other.
 6. A vane pump with a variable discharge volume according to claim 1, further comprising a suction side plate which forms a suction passage for guiding a suction of a compressed medium into the compression chamber and is formed at one side of the cam ring; and a discharge side plate which forms a discharge passage for guiding the discharge of the compressed medium compressed in the compression chamber and is installed opposite to the suction side plate about the cam ring. 